Immobilization of Papain by Macromolecular Crowding in Mesopores under Microwave Irradiation

To improve the immobilization of papain, papain was immobilized on the mesocellular siliceous foams (MCFs) by macromolecular crowding under microwave irradiation. It was observed that the immobilized enzyme exhibited the highest catalysis activity when papain was co-immobilized on MCFs with bovine serum albumin (BSA) and the ratio of enzyme to support at 0.4 (ω). The observed activity of dry immobilized enzyme was 419.1 U/mg, the relative activity and activity yield of immobilized enzyme 126.0% and 119.1%, respectively, when the ratio of BSA to papain was 5%(ω). The main factors influencing the activity of immobilized enzyme were orderly the amount of papain, ratio of BSA to enzyme, power input of microwave and pH. The optimum pH and temperature of immobilized enzyme were 7.0 and 75°C, respectively. The co-assembled papain with BSA was more resistant to heat than free enzyme and the papain assembled solely in MCFs. Its residual activity was still maintained as 88.2% of the initial activity after heating at 80°C for 3 h.